Magnetic susceptibility in Ti-(Cr, Mn)-Si-O 1/1 crystal approximant as a function of oxygen concentration - No evidence for a minimum in N(E_F)

To examine the possible roles for oxygen in the formation of the icosahedral and crystal approximant phases in Ti-TM-Si alloys (TM = V, Cr, Mn, Fe), the magnetic susceptibility was measured in the α(TiCrSiO) and α(TiMnSiO) 1/1 crystal approximant phases. The measured magnetic susceptibility, χ, for α(TiCrSiO) is nearly independent of temperature over the range 6-300 K, showing no measurable Curie-Weiss component. The susceptibility of α(TiMnSiO) contains a small Curie-Weiss component corresponding to a local-moment (j = 5/2) from only a small fraction (∼0.2%) of the Mn. The electronic density of states at the Fermi energy, N(E_F), estimated from the susceptibility contribution of the conduction electrons, changes monotonically with increasing oxygen in both alloys. This suggests that phase stabilization by oxygen does not arise from a Hume-Rothery-type mechanism in these alloys.